To go back to the beginning, the first thing you do is tap on the star in the upper left-hand corner.

Then...1. Tap on the little nest icon with the arrow.2. Choose the leftmost little screen from the ones at the bottom there—Part 1. Tap the middle of the screen and then tap the checkmark to load the save.

It works the same way if you want to load any of the other parts—choose the part you want from the ones at the bottom there (parts 1 through 9 in order from left to right).